Irvine has been satisfied with Mulumbu's reaction to finding himself out of the starting XI.
"We haven't even had a conversation about it, he knows what happened, he knows he went out of the team because of injury and knows that James Morrison has stepped in the team and played really well," Irvine told the WBA website.
"And so he has now got to wait for his chance to come along. That's just part of being a player. There is a squad to cover for injuries and you daren't get injured.
"Youssouf is a great lad and absolutely no problem where that's concerned.
"I think he was probably a bit disappointed with how he played when he came on last weekend (at Liverpool), but he is absolutely no problem.
"He has not changed in any way, he's a lovely lad around the place, he has got an infectious personality and is good on the training ground."
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